Tropical Storm FLORENCE

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Tropical Storm Florence Discussion Number 64
NWS National Hurricane Center Miami FL AL062018
500 AM EDT Sat Sep 15 2018
Florence is slowly weakening while its center remains inland over
extreme eastern South Carolina. However, WSR-88D Doppler radar
still shows some intense bands of convection over the eastern
portion of the circulation, and these bands have been training over
the coast of North Carolina overnight. Based on current Doppler
velocities of 55-60 kt at around 5500 ft, the current intensity is
set at 45 kt. The system should continue to weaken as it moves
farther inland today, and it is anticipated that Florence will
become a tropical depression tonight. The official intensity
forecast is similar to the Decay-SHIPS model guidance through
around day 3. By days 4 and 5, the post-tropical cyclone is
forecast to strengthen somewhat due to baroclinic processes after
moving off the New England coast and passing near southern Atlantic
Canada.
Radar and satellite fixes indicate that Florence continues its
west-southwestward motion at around 255/4 kt. A mid-level high
pressure area to the northwest of Florence is forecast to shift to
the north, northeast, and east of the cyclone over the next couple
of days. As a result, Florence should turn northwestward and
northward, and then north-northeastward through 72 hours. Late
in the forecast period, the system is expected to accelerate
east-northeastward in the mid-latitude westerlies. The official
forecast is somewhat faster than the previous one at days 4 and 5
but is in good agreement with the latest global model runs.
Although coastal storm surge flooding will gradually subside
today, extremely heavy rainfall will continue to be a serious
hazard associated with slow-moving Florence. More than a foot of
rain has already fallen across portions of southeastern North
Carolina, and more rain is still to come, which will cause
disastrous flooding that will spread inland through the weekend.
Key Messages:
1. Life-threatening storm surge will continue along portions of
the North Carolina coast through today, and also along the Neuse
and Pamlico Rivers in western Pamlico Sound, where rainfall and
freshwater flooding will also contribute to high water levels.
Dangerous storm surge could also affect portions of the northeast
coast of South Carolina coast today.
2. Life-threatening, catastrophic flash floods and prolonged
significant river flooding are likely over portions of the
Carolinas and the southern to central Appalachians from western
North Carolina into west-central Virginia and far eastern West
Virginia through early next week, as Florence moves slowly inland.
In addition to the flash flood and flooding threat, landslides are
also possible in the higher terrain of the southern and central
Appalachians across western North Carolina into southwest Virginia.
3. Tropical storm conditions will continue along the coast within
the tropical storm warning area and also well inland across portions
of South Carolina and North Carolina today.
4. Large swells affecting Bermuda, portions of the U.S. East Coast,
and the northwestern and central Bahamas will continue this week,
resulting in life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS
INIT 15/0900Z 33.6N 79.5W 45 KT 50 MPH
12H 15/1800Z 33.6N 80.2W 40 KT 45 MPH...INLAND
24H 16/0600Z 33.9N 81.3W 30 KT 35 MPH...INLAND
36H 16/1800Z 35.1N 82.4W 25 KT 30 MPH...INLAND
48H 17/0600Z 37.0N 83.5W 25 KT 30 MPH...INLAND
72H 18/0600Z 40.5N 80.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 19/0600Z 43.5N 68.0W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 20/0600Z 47.0N 54.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
$$
Forecaster Pasch
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